MENDELISM AND SEX 133 



maleness and hermapliroditism. These cells when 

 they develop into individuals will produce unisexual 

 males, because both unisexuality and maleness are 

 dominant. The second possible result will be 

 attained in the latter case, when fertilised cells 

 having the composition of femaleness and her- 

 maphroditism are formed. These cells will give 

 rise upon development to unisexual female in- 

 dividuals, because unisexuality is dominant over 

 hermaphroditism. Thus two kinds of individuals 

 are expected on this interpretation, unisexual males 

 and unisexual females. And the experimental results 

 do, as we have seen, confirm this Mendelian ex- 

 pectation. 



Now we will take the reciprocal cross as shown in 

 case No. 1 in the table. Here again we meet with 

 the undifferentiated hermaphroditism of B. alba, 

 but now carried in its pollen-cells. In this cross, 

 then, only one result, and not two, as in case No. 2, 

 will occur : the egg-cells carrying femaleness alone 

 of B. dioica will be fertilised by the pollen-cells of 

 B. alba, which are carrying hermaphroditism alone. 

 And since unisexuality is dominant to hermaphro- 

 ditism, all individuals produced by this cross will 

 manifest the unisexual female character. Hence, 

 our Mendelian interpretation expects females only to 

 result from such a cross. And experiment has 

 shown that such is the case. 



While the Mendelian interpretation devised by 

 Correns does undoubtedly enable us to give an 



